A semiconductor logic unit performs various operation processings under control of a system program. When a scale of the system program is large, an external memory device, for example, a magnetic disk, an optical disk, or the like is used for a storage location for the system program. When the scale of the system program is small, a non-volatile memory device fabricated on other substrate different from a substrate on which an operation processing section is formed for the storage location for the system program is used. One of typical examples of the non-volatile memory device is a flash memory in which, for example, a floating-gate type device accumulating charges in an electrode or a silicon-nitride trapping device capturing charges in an insulation film is used. Further, when the scale of the system program is small and it is necessary to reduce a size of the system itself, a non-volatile memory device fabricated on the same substrate on which the operation processing section has been formed for a storage location for the system program is used. As a semiconductor logic unit including non-volatile memory devices on the same substrate in a mixed manner, there is, for example, an IC (Integrated Circuit) card micro controller or an embedded micro controller.
In recent years, as one of memory cell techniques attracting attention to a new electrically rewritable non-volatile memory device, there is a phase change memory device. The phase change memory device is a phase change memory device in which chalcogenide used in, for example, CD-RW (Compact Disk Rewritable), DVD-RW (Digital Versatile Disk Rewritable), DVD-RAM (Digital Versatile Disk Random Access Memory) or the like, all of which are a rewritable optical memory medium, is applied to a memory device. The principle thereof is to utilize an amorphous state where electrical resistance is relatively high and a crystal state where electrical resistance is relatively low as memory information to read the memory information as an electric signal, and rewriting of the memory information plural times is made possible. The amorphous state and the crystal state are selectively produced by adjusting heat imparted to the memory device and a cooling rate of the memory device. That is, the amorphous state is formed by heating a phase change material up to a melted state thereof and the cooling it rapidly. The crystal state is formed by heating the phase change material up to the melted state thereof and then cooling it gradually or by maintaining a formed amorphous state at a crystallization temperature and then cooling it. Since the phase change memory device has such a merit that a fabrication process thereof is simpler than that of a conventional non-volatile memory device such as a flash memory, and since a memory device itself can be made fine, fabrication thereof at a low cost is expected.
For example, a phase change memory device in which a process temperature is not restricted when being fabricated and fabrication thereof is simple, and its fabrication method have been disclosed (see Patent Document 1, for example). A memory device structure in which a phase change material in a phase change material memory device structure can be more efficiently heated and a method for forming it have been disclosed (see Patent Document 2, for example).
Patent Document 1: Japanese Patent Application Laid-open Publication No. 2004-153047
Patent Document 2: Japanese Patent Application Laid-open Publication No. 2003-332530